I have a myson 3 port diverter valve which almost works ok - it turns to central heating or hot water and central heating by motor. When central heating is turned off though the spring does not return the valve to the hot water only position UNTIL the fuse is switched off. If the central heating is just switched off by the programmer or by the thermostat an electrical buzzing can still be heard in the actuator and it gets hot. As I know the programmer and thermostat are working correctly, I assume it is the actuator itself where the fault lies. Any opinions would be welcome before I buy a new actuator. Thanks